Hide glue manufacture



U ed States Patent 2,741,515 ohms 'MANUFAKE'FUR E" Haven: 1.. Ken, Clarendon mus, t an A. riemihaii,

This invention relates "to an iii-trot ed pi'ocess for the inaniifactuie er hide glue. It deals with a process for pre aring salted hide foi glue extriietion. More parneula' ry it relates to the use bf micro-organisms in conditioning salted hide for glue extraction. I

Hide glne is customarily prepared heat the scraps t'riihrhed from salt cured hides. Hides fi'h'm freshly slaughtered animals are cured preparatory to the tanning iipe'ration by storing in hide cellars for a period of from 30 'to 60 days The hide cellars are maintained at a temperature f about 50 F. and the hides are stacked in piles with a layer of rock salt between "the individual hides. When the curing is eemple'te the hides are trimmed, bundled and shipped to the tahnery. The map pieces trimmed from the cured hides are then utilized as the raw material for the manufacture of hide th a In the general practice the salted hide scraps are washed free of salt and dirt and are covered with a saturated lime solution for a period of from 60 days in summer to 120 d ys in colder weather, During this holding period it is necessary re change the limeliquor several tiihes and to turn the hides frequently.

When the hide is suificiently eehaitibhed fe gn-1e traction it is subjected to a prolonged washin opera' tioh to remove lime and finally acidified it a pH or about 6.0. It is then washed back to approximately a neutral pH value and drained of the wash water. The hide is then ready for the glue extraction. 7

The hide is covered with hot water and the temperaare held at about 65 C. for a period of several hours. This ei'itract then removed and the hide is covered with a fresh cooking water which this time is maintained at about 75' C., again for several hjours. The entraction is repeated at temperatures of 85 C., 100 C. and 100 C. The glue li uors-from each extraction the ltept. separate and are each centrifuged, jetted and dried. The dried glue from each extraction may be packaged or the various batches may be blended with other glues to form a glue with the physical characteristics desired.

The lime pretreatment is believed tb soften the keratinous outer layer of the hide scraps and to dis- "solve albumins and mucihs besides opening up the inner hide structures for the entrance of the glue eiitracting waters. Whatever may be the mechanism of the process, it is well known that it is impossible to extract a satisfactory glue from untreated hide by boiling with water, and some type of conditioning of the hide is necessary.

While the lime treatment of hides has long been i general use, this method is subject to several serious disadvantages. The long holding period requires that a large inventoiy be maintained in process and that extensive treating facilities be provided. The stock must be turned frequently and the lime slurry must be drained and replaced with new solution several times thereby adding to the cost of both labor and material requireihnis er the process; During the pretreatment conidiable water is necessarily drained from the stock earr'yih'g with it soluble proteins, hair and emulsified fats, together with calcium soaps. This not only represents a waste of valuable material but also creates sewage disposal problems. Furthermore the glue obtained from lime treated stock is unsuitable for uses demanding a clear product and the total yield of glue obtained is low.

An object of the prese'nt invention is to previde a process in which salted hide stock is prepared for glue entr' action with a minim' m of time and expense. A further object is to provide a process in which higher yields of glue of improved quality may be obtai'ried. Another object is to prevent loss o f protein during the hide conditioning process. A still further dbject is to provide a process in which by-p roduct protein as a quality suitable 'for animal feed is obtained and in which the hair obtained from the hide scrap may he saved in a salable condition. These and other objects will become apparent as the specification proceeds.

We have discovered that salted hide may 'efiectivelly be prepared for glue extraction without the necessity df the prolonged lime treatment if the hide pieces are 'suhjected to the action of the naturally occurring salt resistant micro-organisms found on cured hides. Under the conditions present during hide curing yeasts of the genera Mycoderma (Sp.) and Torulopsis (Sp;) predomiiiate and we have foundthat exposure of the hides to the action of these yeasts is e most effective pretreatment er hide for glue extraction. Ve do not know exatitl'y what changes are hrou'ght about in the hide steer by the action of these micro-organism's, bet in some manner they render the hide susceptible to the entrance or Water during the emeetieh step and in the conversion of the hide collagen to glue.

Iii one embodiment of the itivehtion hide scraps which have been trimmed fr'oih hides cured in the conventional manner are Washed in running Water to remove the dirt and salt. The washed hide pieces are covered with Water and subj'ectedto the action or the salt-resist'adt micro-organisms naturally occurring on the cured hide. After a s'iiitable length of time and when the hides have been adequatel conditioned the water is drained from the treated hide ieces and 'glue ezktraeted in the conventional manner.

The action of the micro-organisms on the hide is complex and is not clearly understood. However ivi'tlr out the pretreatment it is not possible to produce a recogniiable quantity of glue in hot-water extracts of hide while glue is readily extracted following this treatmerit. In some manner the microeo'rganisms change the hide into proper condition for the removal of glue and we use the term conditioned to describe the etfeet of this treatment. As used-in this specification, the term conditioned therefore refers to a treated state in which collagen-bearing material is rendered conducive to the hot-water extraction of glue.

In preparing salted hide' scraps for treatment in the process of the present invention the pieces are first freed of salt and dirt. We find that washing for 24 hours in running water issufiicient for this purpose;

Following the washing the hide pieces are covered with clear water and left to stand. To prevent infection of the treating bath by air-bbrne molds and purie'factii e bacteria. we adjust the pH to the range of pH 1.5 to 3.5. At pH values below 1.5 we finclthat the yeast Culture is killed while if the pH is permitted to go above 3.5 airbourne mold contamination occurs. We prefer to maitithin the pH in the range of 2.0 to 2.5. In our preferred operation we add 'suflieient concentrated hydrochlorie'aid to adjust the pH to ahout 2.0 The pH is determined several times daring the first day with'suifitiient additional acid stirred in as may be nstuji to maintain a 5H of between 2.0 and 2.5. As the treatment proceeds the bath approaches equilibrium and pH adjustments need film is the surface growing yeast Mycoderma (Sp.). At

this time the hide hair slips easily and may readily be pulled.

Following this initial stage, the film forming yeast v gradually disappears from the bath and is replaced by the second yeast Torulopsis (Sp.). In 'this stage of the treatment the hide undergoes further change as the conditioning action is completed. When the keratin layer of the hide can be peeled with the thumb-nail and the hide pieces easily torn by hand, we consider the stock sufiiciently conditioned and it is removed from the treating bath for glue extraction.

The time of treatment to condition hide pieces may be varied through a wide range. We prefer to continue the treatment for about 3 Weeks or more and have found a 21 day period of treatment entirely satisfactory. Over this length of time and under the conditions present the hide microorganisms greatly increase in number and the hide is sufliciently conditionedfor glue extraction. If desired, the conditioning action may be intensified by augmenting the natural occurring hide organisms with inoculations .of cultures obtained from other baths.

The hide pieces may remain in the bath for much longer periods without harmful effect to the glue quality but no particular advantage is gained by prolonging the period of treatment beyond 21 days.

Highest quality glue is obtained from neutral or weakly acid solutions so we prefer to neutralize the conditioned hide stock before the hot water glue extraction is begun. Any suitable alkali may be used for this purpose. We have found that the glue quality is improved when ammonia is employed as the neutralizing agent and we prefer to use concentrated ammonium hydroxide. The conditioned hide is covered with fresh water, concentrated ammonium hydroxide added, and the hides allowed to remain in the solution for 24 hours. We find that adequate neutralization is obtained when the ratio of 3 cc. of concentrated ammonium hydroxide to each 100 grams of conditioned hide stock is employed. Follow ing neutralization the stock is ready for glue extraction.

The conditioned and neutralized hide stock may be treated for the extraction of glue using any conventional glue cooking method. We prefer to employ 5 separate cooking waters, each being at a successively higher temperature. In one embodiment, for example, we maintain temperatures of 65 C., 75 C., 85 (3., 100 C., and 100 C. We find thatthc glue is more readily extracted from hides which have been conditioned in accordance with the process of the present invention and that therefore heating at each temperature for a period of about 3 hours is all that is necessary in order to extract substantially all of the glue from the hides. The glue liquor from each cooking is decanted in turn from the hides and is dried using conventional methods.

When using the conventional saturated lime slurry pretreatment method, the glue extracted at each temperature including the initial low temperature cooking is clouded and turbid, indicating that both the epidermal layer and the collagen break down at once. Moreover the extractions at the lower temperatures which produce the highest quality glue yield only a small portion of the total glue obtained. With our process of micro-organism conditioning the glue extracted at all temperatures up to boiling is clear and unclouded. In addition micro-organism conditioned hides yield a greater percentage of the glue present at the lower extraction temperatures thereby providing increased yields of glue having superior quality.

While our invention is not limited by any theory of explanation we believe that the improved glue quality and increased yields resulting from the practice of the angers .ent in the hide pieces, thus permitting easier penetration of the glue extraction waters to the inner hide structure.

It is a further advantage of our process that theconditioning action is carried out in an acid solution. Glue quality is improved if the extraction is carried out under slightly acid conditions and the glue is more easily extracted, that is in a shorter cooking period, when acid conditions prevail. In the process of the present invention we add ammonium hydroxide or other alkali to neutralize the conditioned stock and we believe that the inner portion of the hide structure may remain slightly acid even after the neutralizing step has been completed. Under these conditions the cooking waters hydrolize the innermost collagen first giving a high yield of superior quality glue at the lower cooking temperatures and after a shorter cooking period. As an example of the advantage enjoyed by our process, we are able to increase the glue yield by 45% over that obtained from hides conditioned by the conventional lime slurry method even though we employ only 15 hours of heating to complete the extraction as contrasted with the heating for a period- Example I Ten pounds of trimmings from salt cured cattle hides were washed in running water for 24 hours to remove the salt and dirt. The washed'hide pieces were covered with 5 gallons of water and 50 ml. of concentrated hydrochloric acid was added. The pH after the addition of the acid Was 2.3. Periodically the pH was determined and .suflicient acid added to maintain the pH between 2.0 and 2.5. After 5 days the surface of the bath was covered with a wrinkled gray film and the hide hair slipped easily. After the 21st day of conditioning the hide was removed from the bath and weighed up at 7304 grams. The pieces were covered with water and 3% or 219 ml. of concentrated ammonium hydroxide was stirred into the lot. The stock remained in the ammonium hydroxide solution for 24 hours and was then removed for glue cooking operations.

Glue extractions were made at to F, to F., to F, 212 F. and 212 F. Fresh extraction waters were used for each heating and the temperature was maintained at each temperature range for 3 hours. The glue liquors from each cooking were removed from the stock, centrifuged, jelled and dried.

The yield of glue was 21.6% on an as received basis. The average jell strength of the glue was 316 grams and the average viscosity 142 millipoises.

Example ll Thirty pounds of salted hide scraps were washed in running water for 24 hours to remove the salt and dirt. The washed hide scraps were covered with 15 gallons of water and 150 ml. of concentrated hydrochloric acid was added' The pH after the addition of acid was 2.0. Additional acid was added as necessary to maintain the pH between 2.0 and 2.5. After 26 days some of the hide pieces were removed from the bath and weighed up at 11,579 grams. These pieces were then covered with water and 3% or 350 ml. of ammonium hydroxide was stirred into the lot. After 24 hours the stock was removed and glue extractions were made following the pro cedure of Example I. The yield of glue was calculated as 24.9% based on an as received basis. The average jell strength was 317 grams and the average viscosity 135 millipoises.

Example III 7 The remaining portion of the hide pieces from Example II were allowed to remain in the conditioning bath for a total of 68 days. Following the conditioning operation the stock was cooked for glue extraction. The glue obtained was of high quality and the viscosity values were not adversely affected by the prolonged conditioning treatment.

While in the foregoing specification, we have set out specific examples in considerable detail for the purpose of illustrating one mode of practicing the invention, it will be understood that such details may be varied widely by those skilled in the art without departing from the spirit of our invention.

We claim:

1. A process for conditioning hide for glue manufacture which comprises subjecting salted hide stock previously washed free of salt and dirt to the action of naturally occurring, living hide micro-organisms at a pH offrom about 1.5 to about 3.5 for a period of about 21 days.

2. A process for conditioning hide for glue manufacture which comprises washing salted hide stock free of salt and dirt, subjecting the washed hide to the action of Mycoderma (Sp.) and Torulopsis (Sp.) at a pH of from about 1.5 to about 3.5 for a period of about 21 days.

3. A process for manufacturing hide glue which comprises subjecting salted hide stock previously washed free of salt and dirt to the action of naturally occurring, living hide micro-organisms at a pH of from about 1.5 to about 3.5, adding alkali to neutralize the acid, and extracting glue from the stock with hot water.

4. A process for manufacturing hide glue which comprises subjecting salted hide stock previously washed free of salt and dirt to the action of naturally occurring, living hide micro-organisms at a pi-I of from about 1.5 to about 3.5 for a period of about 21 days, adding ammonia to neutralize the acid and extracting glue from the stock with hot water.

5. A process for conditioning hide for glue manufacture which comprises washing salted hide stock free of salt and dirt, subjecting the washed hide to the action of Mycoderma (Sp.) and Torulopsis (Sp.) at a pH of from 2.0 to 2.5 for a period of 21 days.

6. In a process for manufacturing glue from salted hide the step of subjecting the previously washed hide to the action of naturally occurring, living hide micro-organisms at a pH of from about 1.5 to about 3.5 for a period of about 21 days.

7. In a process for manufacturing glue from salted hide scraps, the step of subjecting the previously washed hide to the action of the yeasts Mycoderma (Sp.) and Torulopsis (Sp.) at a pH of from about 1.5 to about 3.5 for about 21 days.

8. In a process for manufacturing glue from salted hide scraps, the step of subjecting the previously washed hide to the action of yeasts Mycoderma (Sp.) and Torulopsis (Sp.) at a pH of from 2.0 to 2.5 for at least 21 days.

9. In a process for manufacturing glue from salted hide scraps, the step of subjecting the previously washed hide to the action of the yeasts Mycoderma (Sp.) and Tomlopsis (Sp.) at a pH of from 2.0 to 2.5 for 21 days.

References Cited in the file of this patent UNITED STATES PATENTS 

2. A PROCESS FOR CONDITIONING HIDE FOR GLUE MANURACTURE WHICH COMPRISES WASHING SALTED HIDE STOCK FREE OF SALT AND DIRT, SUBJECTING THE WASHED HIDE TO THE ACTION OF MYCODERMA (SP.) AND TORULOPSIS (SP.) AT A PH OF FROM ABOUT 1.5 TO ABOUT 3.5 FOR A PERIOD OF ABOUT 21 DAYS. 